1. Field of the Invention
The present invention relates to a coordinate input apparatus. More particularly, the present invention relates to a coordinate input apparatus provided with means for preventing a moving cursor from going too far when a stick-type operation section provided in a keyboard device or the like is operated to cause the cursor within the display section to move.
2. Description of the Related Art
Hitherto, as keyboard devices, there are known a type having only various operation keys arranged in a predetermined sequence in the operation section, and a type (hereinafter, this type will be referred to as a "keyboard device with a stick-type operation section") having such operation keys and one stick-type operation section (stick pointer) at a predetermined position among the operation keys.
Meanwhile, in a known keyboard device with a stick-type operation section, a distortion gauge (a total of four distortion gauges) is bonded onto each side of the base portion of the stick-type operation section along two directions, i.e., along the X and Y directions, intersecting at right angles to each other. These distortion gauges are structured in such a way that two distortion gauges are connected in series between a DC power supply and a ground in each of the X and Y directions, and outputs corresponding to operational pressures (load forces) in each of the X and Y directions are guided out from the connection points of the two distortion gauges which are connected in series. When the tip of the stick-type operation section is pressed in a desired direction by the fingertip of the key operator, the load force applied to the stick-type operation section is applied to the respective distortion gauges in each of the X and Y directions, causing each of the values of these distortion gauges to vary. At this time, changes in these resistance values are detected as voltage changes in each of the X and Y directions, and thus by reading the detection output, load data indicating the load force at the tip of the stick-type operation section is obtained. Then, the obtained load data is subjected to digital conversion and other data processing and is converted into coordinate data within the keyboard device with a stick-type operation section. Next, the coordinate data is transmitted from a communication control section within the keyboard device with a stick-type operation section to a main unit, such as a personal computer, through a cable.
On the main unit side, the coordinate data supplied from the keyboard device with a stick-type operation section is appropriately processed, after which the data is supplied to a display section, causing a cursor displayed on the display section to move. In this case, the movement direction of the cursor is determined in response to the direction of the pressing operation applied to the stick-type operation section, and the movement speed of the cursor is determined in response to the magnitude of a load force during a pressing operation applied to the stick-type operation section.
In the above-described known keyboard device with a stick-type operation section, when the key operator presses the tip of the stick-type operation section in a desired direction, a load force due to the pressing operation is applied to the respective distortion gauges in each of the X and Y directions, causing each of the resistance values of these distortion gauges to vary. Changes in these resistance values are detected as voltage changes in each of the X and Y directions, and are formed into X-direction load data and Y-direction load data. These load data along the X and Y directions are individually converted into coordinate data in accordance with a count value by the cursor movement control section and transmitted to the main unit as described above.
FIGS. 4A and 4B are operation diagrams illustrating an example of a changed state of an operational load force when the stick-type operation section is operated in the above-described keyboard device with a stick-type operation section; FIG. 4A shows a changed state of an operational load force; and FIG. 4B shows an output count value.
As shown in FIGS. 4A and 4B, regarding the output count value of the coordinate data, when operating such that the operation load increases linearly in the first half and decreases linearly in the second half during the operation of the stick-type operation section, a range where an inclination of the increase count value is almost zero, a range where an inclination of the increase count value is small, and a range where an inclination of the increase count value is large appear continuous in the first half where the operational load increases linearly, and a range where an inclination of the decrease count value is large, a range where an inclination of the decrease count value is small, and a range where an inclination of the decrease count value is almost zero appear continuous in the second half where the operational load decreases linearly.
Here, in the above-described known keyboard device with a stick-type operation section, when the cursor on the display section of the main unit is moved by operating the stick-type operation section, there are cases where the cursor does not stop at the desired position and goes too far. Therefore, there arises problems in that it is difficult to perform a desired cursor movement. The causes for such cursor over-movement are attributed to a delay in the transmission of coordinate data to the display section, delays due to the elastic properties of the rubber cap which covers the stick-type operation section and the fingers of the key operator, and the like. These are usually difficult to avoid.
However, some key operators having a great deal of experience make a cursor move to a desired position by reducing pressure to the stick-type operation section before the desired position by taking into consideration the cursor over-movement from the desired position. Such cursor movement operation cannot be performed by everybody easily.